Recently, a laser beam is increasingly used in cutting, welding, and heat treatment of metal members due to cost reduction, factory automation, and quality improvement.
Primary issues required for applying the laser beam are such that energy distribution of the laser beam is uniformized, laser output is controlled so as to maintain a constant heat treatment temperature, shooting speed of the laser beam is optimized so as to satisfy productivity and quality, and energy absorption ratio is maximized. That is, cost reduction and quality improvement can be achieved when applying the laser beam if the primary issues are satisfied.
Herein, joining method for joining two joining members or panels by using the laser beam is divided into brazing and welding.
Firstly, brazing is a metal-joining process where the joining members are not melted but a filler metal is melted since non-ferrous metal or non-ferrous metal alloy (e.g., solder or braze) having a lower melting point than the joining members is used as the filler metal. In this case, the molten filler metal is diffused between the joining members by capillary phenomenon and a base metal constituting the joining members is wet by the molten filler metal. After that, if the filler metal and the joining member are cooled, the joining members are joined.
The laser brazing, compared with spot welding, can enhance degree of design freedom and productivity due to beautiful appearance, reduce cost since there is no need to spray molding or sealer into a joining portion, and improve strength of a vehicle body due to spreading stress of the joining portion. So as to obtain good brazing quality, the panels, focus of the laser beam, and an end of a filler wire should be aligned.
In addition, the laser welding is a metal-joining process where, in a state that two joining members (panels) are overlapped with each other, the laser beam is shot into a welding portion (joining portion) so as to melt the panels. In this case, a molten metal is pushed to an opposite direction of welding progress by a pressure of plasma occurring around a laser welding portion. After that, the molten metal is solidified and a welding bead is produced such that the joining members (panels) are joined by the welding bead.
Quality of laser welding is affected by gap size between the joining members. If sufficient space for expanding gasses to pass does not exist, the gas breaks through or caves the welding bead. Therefore, breakage of the welding portion can occur.
Accordingly, an additional apparatus for applying pressure to or clamping the joining members is essentially required so as to maintain a gap between the joining members.
A laser apparatus used in the laser brazing or welding includes a laser optic head in which a plurality of lenses is provided. The laser optic head is adapted to shoot the laser beam oscillated by the laser oscillator into the welding portion.
According to a conventional laser apparatus, an apparatus for supplying the filler metal is essentially required when the brazing, and the additional apparatus for applying pressure to or clamping the joining members is essentially required when welding. Therefore, initial investment cost can increase.
In a case that the laser brazing and the laser welding are simultaneously used for joining two joining members, one of the brazing and the welding should be performed after the other of the brazing and the welding was performed. Therefore, working hours are very long.
Because the brazing and the welding cannot be performed by one laser apparatus, manufacturing cost can increase.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it can contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.